Many modern medical instruments are comprised of two or more stand-alone components that perform specialized functions. The components may be used alone only if a single function is desired, or the components may be coupled together to form a medical instrument having multi-function capabilities. One example of a multicomponent medical instrument is the LIFEPAK 5.RTM. electrocardiogram monitor and defibrillator produced by Physio-Control Corporation of R. edmond, Washington. The monitor records and analyzes a patient's electrocardiogram (ECG) signal while the defibrillator produces a high energy defibrillation pulse to terminate ventricular or atrial fibrillation. Each component may be used separately when only one function is desired. Alternatively, the monitor and defibrillator can be secured together as a single unit having both monitoring and defibrillation capability.
Mechanical connectors are typically used to secure the separate medical components together. One example of such a mechanical connector is disclosed in U.S. Pat. No. 4,096,856 which is expressly incorporated by reference herein. Although the connector shown in the '856 patent was an improvement to the prior art, the connector was not designed to prevent the coupling of similar but incompatible medical instruments. During emergency situations, it is important that physicians or medical technicians not be able to connect and attempt to operate medical instruments that were not designed to work with each other.